Generally, a method wherein sparks of an ignition apparatus are cut out is used in a rotating speed control apparatus. Ignition apparatuses are mainly classified into a current cut-off system in which the primary energy is stored as magnetic energy by way of the primary current of the ignition coil, and a capacitive discharge ignition (CDI) system in which the primary energy is stored as electrostatic energy when a capacitor is charged to hundreds of volts. In addition, each of the above systems is mainly classified into a magnet ignition type and a battery ignition type in dependence on a difference in the energy source.
In the CDI system, as compared with the current cut-off system, the secondary voltage rapidly rises and the energy discharging time is short. Thus, the CDI system has as features that: the load characteristic to the leakage resistance due to a strain or damage of the plug is good; the charging time of the capacitor can be reduced; degradation in performance upon high-speed operation is small, and the like. Accordingly, this CDI system is frequently used for a racing car or a two-wheeled vehicle.
In a conventional rotating speed control apparatus for an internal combustion engine, there has been proposed the addition of a release apparatus for inhibiting the control of the engine rotating speed by an overspeed preventing circuit (Japanese Patent Application Laid-Open No. 72660/1980), as shown in FIGS. 3, 4A and 4B of the present application. Practically speaking, respective terminals of an ignition circuit of the CDI system serving as a part of an ignition apparatus are arranged on a base board 130 so as to lie in two vertical lines, as shown in FIG. 3. Terminals A and B of an overspeed preventing circuit are normally connected by way of a short-circuit plate 132 as shown in FIGS. 3 and 4A. To inhibit the control of the rotating speed of the engine by the overspeed preventing circuit, the attaching position of the plate 132 is shifted to the left to thereby open the circuit, as indicated by broken lines in FIG. 3 and as shown in FIG. 4B.
However, this method has drawbacks, including the fact that it is necessary to detach the terminals fixing the short-circuit plate in order to move it, which takes a long time and is troublesome, so that it could take too long in the event of emergency. There is also another drawback in that it is impossible to release the plate from the driver's seat or the like by way of a remote control operation.
Further, when the rotating speed of the engine is to again be controlled by the overspeed preventing circuit, it is necessary to manually shift the short-circuit plate back to its original position after removing the terminals and to then fix this plate in position with the terminals, which takes a long time, like the release. Consequently, once the speed control has been inhibited, the replacement of the short-circuit plate is troublesome and there is thus a risk that it will not be replaced and the engine will subsequently be used in the state where overspeed projection is inhibited, even in a case where there is no need to inhibit the speed control and the control of the engine speed by way of the overspeed preventing circuit might have been purposely stopped.